A well known and practiced method of obtaining subterranean core samples is to use a split barrel core sampler in conjunction with a hollow stem drilling auger bit or in conjunction with a drive hammer. Subterranean core samples provide valuable information to those in the environmental and geotechnical industries. The core sampler is forced downward into the subterranean surface, causing the core sample to be forced upward into a passageway in the hollow barrel of the core sampler. After the core sample has been gathered, the core sampler is retrieved from the subterranean location and removed from the drilling string to retrieve the core sample. A core sampler with a characteristic split barrel facilitates the removal of the core sample after the core sampler has been removed from the drill string.
It is advantageous to develop methods and devices that minimize the amount of time and manpower necessary to retrieve a gathered core sample. This is because the drilling rig is shut down during this time, so drilling efficiency is directly impacted by the core sample retrieval. Thus, shortening the retrieval time results in higher drilling rig operational efficiency, meaning proportionally more time at the drill site is spent on productive activities like drilling or sample collecting, rather than on core sample retrieval.
There is a need in the industry to improve the conventional means of attaching drilling and sampling tools to a drilling rig drill string. The commonly used means of threadingly engaging these members is cumbersome, typically requiring at least two operators with large wrenches to break the threaded connector loose. Further, the nature of a threaded connection is inherently counter-productive to maximizing the efficiency of the retrieval process, because the rotary action of the drilling string tends to over-tighten the joints. Moreover, a threaded connection is subject to wear and tear with age, especially in the aggressive downhole environment at hand, and as such, connections become progressively more difficult and time consuming to make and break. Finally, threaded connections are subject to catastrophic failure when they become cross-threaded or stripped, and repair or recovery of a stripped or cross-threaded joint can easily result in many man-hours of rig downtime.